A filling device (filler) fills cans with a liquid such as beer. The cans are supplied to the filling device by a conveyor (convey device) along a convey path. Supply of the cans to the filling device is performed and stopped by a can control apparatus arranged on the convey path.
FIG. 1 is a view schematically showing a conventional filling device and can control apparatus. Cans 10 are continuously conveyed by a conveyor 6 along a convey path while they are guided by guide members 4a and 4b. A timing screw 3 and star wheel 2 rotate in synchronism with a filling unit 1. The timing screw 3 has a helical engaging portion (when expressed from between engaging portions) formed on its entire circumference to engage with the side surfaces of cylindrical cans 10. When the cans 10 reach near the upstream end portion of the timing screw 3, they engage with the helical engaging portion and are conveyed toward the star wheel 2 as the timing screw 3 rotates. At this time, the timing screw 3 and star wheel 2 are synchronized so that the cans 10 are transferred into semicircular recessed engaging portions in the star wheel 2.
When supply of the cans 10 to the timing screw 3 (filling unit 1) must be stopped, the cans 10 are sandwiched by a pair of opposing stopper members (can control apparatus) 5a and 5b, so that conveyance of the cans 10 can be forcibly stopped. In this state, typically, the conveyor 6 operates continuously. Hence, a frictional force acts on the cans 10 which are stopped as they are sandwiched by the stopper members 5a and 5b, and cans 10 which follow them.
When supply of the cans 10 to the timing screw 3 (filling unit 1) is to be resumed (started), restriction or interception of the cans 10 by the pair of opposing stopper members 5a and 5b may be canceled. Then, the cans 10 start moving by the conveyor 6 again toward the downstream timing screw 3 along the convey path.
In addition to the mechanism in which both the stopper members 5a and 5b are pushed toward the cans 10 to sandwich them, another mechanism is also available in which only one stopper member is pushed toward the cans 10 to sandwich them.
The conventional can stopping apparatus as described above has various problems, and typical ones will be described hereinafter.
Conventionally, the stopper members 5a and 5b are driven regardless of the positions of the cans 10, and sandwich the cans 10 to stop them. Accordingly, as shown in, e.g., FIG. 2, if the stopper members 5a and 5b are not operated at a good timing and sandwich a leading can 10a insufficiently, the leading can 10a may sometimes move through downward, i.e., toward the timing screw 3 by the movement of the conveyor 6.
The leading can 10a is conveyed toward the timing screw 3 with a distance being formed from a preceding can 10b. The distance depends on various types of parameters, e.g., the positional relationship between the can 10a and the stoppers 5a and 5b when the stoppers 5a and 5b are operated, the convey speed of the conveyor 6, and the frictional force between the conveyor 6 and can 10a, and is accordingly unpredictable and changes each time.
When the can 10a is to slip out from the stopper members 5a and 5b, if it is inclined, as shown in FIG. 3, it is sometimes supplied to the timing screw 3 in a swaying state.
As described above, the can 10a slipping out from the stopper members 5a and 5b can be supplied to the timing screw 3 at a wrong timing because the distance between the can 10a and the preceding can 10b is not maintained at a predetermined distance (for example, an integer multiple of the diameter of the can 10). Then, as schematically shown in FIG. 4, the helical tooth portion formed on the timing screw 3 may bite into the trunk of the can 10a to deform or break the can 10a. If the can 10a is broken to leave its pieces on the convey path, the pieces can damage or dent the subsequent cans, or enter the timing screw 3 or a mechanism downstream of it to cause operation errors.
Similarly, when the can 10a is supplied to the timing screw 3 in a swaying state, it may be deformed or broken. When the sway of the can 10a is large, the can 10a may fall. When the can 10a falls over, it may be supplied to the timing screw 3 in a lying state to cause operation errors of the timing screw 3.